Explanation:

- The context describes a current that can carry away big tree trunks, indicating strength and force.

- Option 1: Compelling - This is typically used to describe an argument or character that is convincing or interesting, not a physical force.

- Option 2: Powerful - This word appropriately describes a strong current capable of moving large objects like tree trunks.

- Option 3: Powerless - This is the opposite of what the context implies; a powerless current couldn't move heavy objects.

- Option 4: Gentle - This implies a soft or mild current, unsuitable for carrying away large objects.

- Option 5: Persuasive - This is akin to compelling and is used more for arguments or speech rather than physical force.